Влияние ионной подсистемы на термоэлектрический эффект в коллоидных растворах

The thermoelectric effect is investigated in mixtures of colloidal solutions with ionic electrolytes in the initial state, when the formation of concentration gradients under the influence of an inhomogeneous temperature field can be neglected. Based on experimental measurements in mixtures with different concentrations of colloidal particles and ions, the conditions under with the coefficient of thermoelectric EMF is determined by the ion subsystem and under which the main contribution to the value of the thermoelectric force is made by colloidal particles are determined.

Genesis and structure of the iron ore deposit of the Cape Iron Horn

Статья посвящена железорудному месторождению, представляющему собой пласт оолитовых (бурожелезняковых) руд железа, который выходит на дневную поверхность на мысе Железный Рог на берегу Таманского полуострова. Мыс имеет протяженность 1,3 км с запада на восток и высоту 55 м над уровнем моря. Склон мыса разбит многочисленными трещинами из-за эрозионного воздействия ветра и морской воды, по которым происходит откалывание оползневых тел. Актуальность работы. Железорудное месторождение на мысе Железный Рог Таманского полуострова известно с конца 19 века, в настоящее время (с 1984 года) ему присвоен статус памятника природы, из-за чего добыча сырья запрещена на всей охраняемой территории, составляющей 19 га. Однако минералогия, палеонтология и особенности геологии данного месторождения изучены недостаточно. Таким образом, представленная статья призвана в какой-то степени восполнить этот пробел. Целью проведенных исследований является выявление особенностей геологического строения, минерагении и генезиса железорудного месторождения на мысе Железный Рог Таманского полуострова. Методы работы. Основу работы составляют образцы, отобранные авторами во время полевых работ на мысе Железный Рог с июня по июль 2021 года. При выполнении работы были описаны 15 образцов, а также идентифицированы палеонтологические находки и определен их примерный возраст. Результаты работ. Установлено, что бурые железняки залегают в толще серых глин железнорогской свиты (N1-2žr) и совпадают с ними по возрасту, что подтверждается палеонтологическими находками. В разрезе были найдены только те минералы, в состав которых входит железо: борнит, вивианит, лимонит, халькопирит. В работе проанализированы структурно-текстурные особенности пласта и вмещающих его пород, а также ассоциации найденных минералов, на основании чего сделаны выводы, что данный пласт железных руд относится к хемогенному осадочному типу месторождений, образованному из коллоидных растворов The article is devoted to an iron ore deposit, which is a layer of oolitic (brown limestone) iron ores, which comes to the surface during the day at Cape Iron Horn on the shore of the Taman Peninsula. The cape has a length of 1.3 km from west to east and a height of 55 m above sea level. The slope of the cape is broken by numerous cracks due to the erosive effects of wind and sea water, along which landslide bodies are chipping away. Relevance.The iron ore deposit at Cape Iron Horn of the Taman Peninsula has been known since the end of the 19th century, currently (since 1984) it has been given the status of a natural monument, which is why the extraction of raw materials is prohibited in the entire protected area of 19 hectares. However, mineralogy, paleontology and features of the geology of this deposit have not been studied enough. Thus, the presented article is intended to fill this gap to some extent. The Aim of the research is to identify the features of the geological structure, mineralogy and genesis of the iron ore deposit at Cape Iron Horn of the Taman Peninsula. Methods. The work is based on samples selected by the authors during field work at Cape Iron Horn from June to July 2021. During the work, 15 samples were described, as well as paleontological finds were identified and their approximate age was determined. Results.It has been established that brown ironstones lie in the thickness of gray clays of the Zheleznogorskaya formation (N1-2žr) and coincide with them in age, which is confirmed by paleontological findings. Only those minerals containing iron were found in the section: bornite, vivianite, limonite, chalcopyrite. The paper analyzes the structural and textural features of the formation and its host rocks, as well as the associations of the minerals found, on the basis of which it is concluded that this iron ore formation belongs to the chemogenic sedimentary type of deposits formed from colloidal solutions

INFLUENCE OF THE POLYETHYLENE GLYCOL MOLECULAR MASS ON THERMAL TRANSITIONS OF NANOSIZED COPPER OXIDE

В данной работе получены образцы наноразмерного оксида меди, стабилизированного полиэтиленгликолем различных марок с молекулярными массами от 200 до 6000 Да. Методом рентгеновской дифрактометрии исследована кристаллическая структура полученных образцов наноразмерного оксида меди. В результате рентгенофазового анализа установлено, что структура образцов представляет собой моноклинную кристаллическую решетку, с пространственной группой C2/ c. Методом фотонно-корреляционной спектроскопии изучено влияние молекулярной массы полимера на размер наночастиц. Анализ результатов исследования показал наличие во всех образцах наноразмерного оксида меди (II), стабилизированного полиэтиленгликолем с различной молекулярной массой, одной фракции частиц, распределение которых по размеру носит мономодальный характер. Установлено, что молекулярная масса полиэтиленгликоля оказывает, влияние на размер частиц CuO в коллоидных растворах, при этом фазовый состав и размеры кристаллитов остаются неизменными. Средний гидродинамический радиус частиц CuO в полученных образцах составляет порядка 140 ± 40 нм. Наименьшие значения гидродинамического радиуса 70 ± 15 нм наблюдаются в образце наноразмерного оксида меди, стабилизированного полиэтиленгликолем с молярной массой 6000 Дa. Методом синхронного термического анализа исследовано влияние стабилизатора с различными молекулярными массами на фазовые переходы образцов при термической обработке. В результате термического анализа установлено, что оптимальной температурой прокаливания порошков наноразмерного CuO является 500°C. In this work, samples of nanosized copper oxide stabilized with polyethylene glycol of various grades with molecular weights from 200 to 6000 Da were obtained. The crystal structure of the samples was investigated by X-ray diffractometry. As a result of the XRD analysis, it was found that the samples have a monoclinic crystal lattice with space group C2 / c . The effect of the molecular weight of the polymer on the size of nanoparticles was studied by the photon correlation spectroscopy method. Analysis of the results showed the presence of one fraction of particles in all samples, the size distribution was monomodal. It was found that the molecular weight of polyethylene glycol has an effect on the CuO particle size in colloidal solutions, while the phase composition and crystallite size remain unchanged. The average hydrodynamic radius of CuO particles in the obtained samples was about 140 ± 40 nm. The smallest hydrodynamic radius of 70 ± 15 nm was observed in a sample of nanosized copper oxide stabilized with polyethylene glycol with a molecular weight of 6000 Da. The effect of stabilizers with different molecular weights on the phase transitions of samples during heat treatment was investigated by the synchronous thermal analysis. As a result of thermal analysis, it was found that the optimum temperature for calcining nanosized CuO powders was 500 °C.

Perioperative infusion therapy

Perioperative infusion support of surgical patients is the main and non-alternative element of treatment. At the same time, the tactics of infusion therapy continues to be the subject of study. Ideas about the optimal quantitative and qualitative composition of the fluid transfused to patients are being revised as ideas about the pathogenesis of critical conditions evolve. The basis of pathogenetic analysis of compensatory hemodynamic capabilities, as a point of application of infusion treatment, previously consisted mainly of invasive monitoring techniques, replaced in recent years by the control of routine parameters with proven high correlation with invasive ones. In current studies devoted to the problems of infusion correction of hemodynamic abnormalities, the most discussed issues are the applicability of isotonic and balanced polyionic crystalloids, less often colloidal solutions in various clinical situations, and the results of such studies do not always allow to unambiguously determine the choice of infusion media, and sometimes simply incomparable. Some researchers advocate the use of isotonic crystalloids, some works prove the best effectiveness of balanced salt solutions. With the volumes of treatment corresponding to the perioperative period, in most studies there are no differences in the effectiveness of the main composite groups of crystalloids at all. We see the reason for this in the peculiarities of randomization methods, when statistical limitations do not allow us to avoid discrete data analysis: their comparative grouping occurs according to the principle of selecting a target parameter, and all the others are classified as auxiliary or secondary. It seems to us that the involvement of arrays of data obtained in real clinical practice as a result of a combination of local theoretical and empirical ideas about corrective treatment regimens correlated with their effectiveness could smooth out the inconsistency of the results of such studies, especially since clinicians have a sample with a volemic load at their disposal, allowing them to predict the hemodynamic reaction of the patient's body to infusion and a set of routine parameters for more fine-tuning of therapy.

Particle dynamics in drying colloidal solution using discrete particle method

We study particle dynamics in drying colloidal solutions using the numerical simulation with discrete particle method (DPM). Simulations of two different systems were conducted; the drying dynamics of monodispersed and binary mixture of colloidal solution, and compared with those from the previous studies. In the monodispersed colloidal solution, the time evolution of particle concentration profile for varying Péclet number was simulated with the same initial particle concentration. In the binary colloidal solution, when the particle size ratio α is 3, three different stratification modes were observed varying Péclet number and initial particle concentration. By comparison, our method was in a good agreement with the existing methods. Additionally, because of the mesh-based Eulerian approach in our model, other various multi-physical phenomena, such as effect of thermal Marangoni or chemical reaction, can be included in an easy way. From the results, we expect that this work can provide a physical insight for predicting the quality of colloidal drying in a complicated situation.

PHOTOLUMINESCENCE OF NANOCRYSTALLINE CdTe, INTRODUCED INTO POROUS SILICON

A method of colloidal synthesis of monodisperse nanocrystals (NC) with high stability, narrow bands of photoluminescence (PL) and high quantum yield has been developed. The process of colloidal synthesis took place at room temperature and for the passivation of NC used a variety of surfactants. The surface of NC CdTe was modified by introducing them into a matrix, organic or crystalline. In our case, the matrix was porous Silicon (PS), that is a composite structure was formed on the basis of the matrix and NC semiconductor. Nanocomposite structures of PS – NC CdTe were obtained by introducing colloidal solutions of NC CdTe into the solid matrix of PS and subsequent processing at a certain temperature regime. The photoluminescent properties of a composite system in which the matrix is microcrystalline PS and the second component is NC CdTe deposited from a colloidal solution of NC CdTe have been studied. The peculiarity of this system is that both components have PL of different intensities.The large difference in PL intensities and different positions of the radiation bands allowed, comparing the PL spectra of the colloidal solution of NC CdTe, PS and NC CdTe – PS at different stages of introduction of CdTe nanoparticles into the porous Silicon surface, to identify the interaction and mutual influence of the two constituent materials. The main disadvantages of the method are its relative novelty, which leads to the need for empirical selection of some parameters of the synthesis. The planned change of properties of PS and colloidal solutions of NC CdTe by variation of technological methods of synthesis and processing methods will allow to control the physical properties of this composite system and use it to develop new principles of design and creation of new generation sensor devices.

Synthesis of metallic aluminum particles by electrolysis in aqueous solution

The present work proposes a method for fabricating metallic Al particles in aqueous solution. An aqueous colloidal solution was prepared from an aqueous aluminum nitrate nonahydrate solution by electrolysis using metallic Al plates as the anode and cathode under ultrasonic irradiation in water at 25–45 °C. The sizes of the particles in the colloidal solutions prepared at 25, 35, and 45 °C were 76.3, 77.0, and 84.7 nm, respectively. The powder obtained from the colloidal solution prepared at 25 °C was not crystalline. By contrast, the powders obtained from the colloidal solutions prepared at 35 and 45 °C had a crystal structure of cubic Al and crystal sizes of 55.7 and 59.3 nm, respectively. Thus, elevated temperatures promoted both particle growth and crystal growth, which was explained by higher temperatures increasing the frequency and energy of particle collisions. The metallic Al particles were chemically stable in both an aqueous solution and the ambient atmosphere. The chemically stable metallic Al particles are expected to be used as sources for fabricating materials related to fuels, energy storage, and pigments.

Kinetics of Silver Accumulation in Tissues of Laboratory Mice after Long-Term Oral Administration of Silver Nanoparticles

Since ancient times, silver has been known for its pronounced bactericidal, antiviral and fungicidal properties. Currently, nanoparticles of this metal are widely used in the food, light and pharmaceutical industries, as well as in medicine. Silver in any form can have a toxic effect not only on pathogens, but also on healthy cells. The biological activity and bioavailability of silver preparations depend on the degree of their solubility in water. In addition, the maximum permissible concentration of soluble forms of silver is an order of magnitude lower than that of insoluble forms. This makes nanoparticles of silver with a hydrophilic coating that form stable colloidal solutions in aqueous media potentially unsafe objects. In this work, we studied the kinetics of the accumulation of silver nanoparticles with an average size of 34 ± 5 nm stabilized with polyvinylpyrrolidone in the organs of laboratory C57Bl/6 mice. The administration of nanoparticles was carried out orally for 30, 60, 120 and 180 days at the dose of 50 µg/day/animal. All the mice developed and gained weight normally during the experiment. No adverse effects were observed. Determination of the silver content in biological tissues of mammals was accomplished by neutron activation analysis. The masses and concentrations of silver in the brain and its different sections (hippocampus, cerebellum, cortex and remnants), as well as in the lungs, testes, liver, blood, kidneys, spleen and heart, were determined. The injection times at which the accumulation curves reached saturation were established. An extremely high accumulation of silver in the testes was shown at 120 days of administration, and a significant accumulation of silver in the lungs and brain was observed. The accumulation of silver in all parts of the brain except the cortex was significant, and its trend was similar to that in the whole brain.

Probing the interactions between dye molecules and metallic nanoparticles - Implications for surface enhanced spectroscopies

<p>The work in this thesis focuses on improving the understanding of two key aspects of the interaction between dye molecules and metallic nanoparticles, with particular relevance to Surface Enhanced Raman Spectroscopy (SERS). This is manifested from two main branches of experimental work; the first is concerned with improving the reproducibility of SERS sample preparation using colloidal solutions while the second focuses on directly measuring the absorption spectra of commonly used dye molecules on the surface of colloidal silver nanoparticles. In the first body of work of the thesis, a major step towards improving SERS in colloidal solutions is achieved by highlighting a crucial, but unnoticed possible source of error for such samples; by comparing average enhancement factor measurements on colloidal solutions prepared using different analyte (dye) dilution methods, it is shown that large dye dilution factors can cause extreme variations in nanoparticle coverage across the entire sample. This not only causes analyte-dependent enhancement factors (which is highly undesirable) but can also lead to false identification of single-molecule SERS experiments using the well established bi-analyte method. The errors associated with large dilution factors are interpreted as a competition between dye diffusion and adsorption kinetics. Time dependent fluorescence quenching measurements and finite element modelling (FEM) in COMOSL show that in any system where adsorption competes with diffusion, large dilution factors should be avoided. A simple protocol of half-half dilutions of analytes is proposed as a standard method to be adopted when preparing colloidal solutions for SERS to ensure uniform distribution of analytes is achieved. The second body of work is an experimental investigation of the modification of the energy levels of commonly used dye molecules adsorbed to spherical silver nanoparticles at sub-monolayer concentrations. Through the use of a novel integrating sphere setup, the absorption spectra of Rhodamine 6G, Nile Blue, Rhodamine 700 and Crystal Violet are successfully measured on the surface of silver colloids at ultra-low concentrations where dye-dye interactions are negligible. These results indicate that for most dyes, absorption pectra on the colloid surface are shifted and/or broadened with respect to the free dye in solution. In the most extreme case, a blue shift of almost 90 nm for Crystal Violet suggests a strong chemical interaction with the silver surface. A Mie theory shell model of dye-coated silver spheres is found to accurately reproduce the measured evolution of absorption spectra as the dye concentration on the colloid surface is increased but overestimates the enhancement in absorption, which is interpreted as a result of the adsorption geometry of dyes on the surface, not captured by the shell model. Finally, through careful wavelength dependent SERS measurements, the SERS Raman excitation profile of Crystal Violet is measured and shown to be closely linked to the modified absorbance as obtained in the integrating sphere setup. A standard optical transform model for computing the Raman excitation profile from the modified absorbance is applied and gives good agreement with the measured SERS data. These results represent a direct indication of chemical modifications of resonant molecules used in SERS studies.</p>